The present application is a continuation-in-part of patent application Ser. No. 07/431,986, filed Nov. 6, 1989 and currently abandoned.
(1) Field of the Invention
The present invention relates to a pneumatic or hydraulic rotary actuator particularly well suited for selectively rotating a ball stopcock of a valve. In particular, the present invention comprises a power cylinder or a diaphragm, each housing a reciprocating piston rod and each being positioned coaxial to the rotary axis of a valve stopcock. The linear piston rod stroke of the actuator is converted by a spindal drive to rotational movement of a driving member that is positively engaged with the valve stopcock. The power cylinder or diaphragm of the actuator may be designed for double action with pneumatic or hydraulic pressure being selectively applied to opposite sides of the piston or diaphragm, or may be designed for hydraulic or pneumatic pressure to be applied to only one side of the piston or diaphragm with a spring counteracting the pressure exerted on the piston or diaphragm.
(2) Description of the Related Art
In a known actuator for the pneumatic operation of valve ball stopcocks, air throttles, and interlocking devices of service doors (DE-OS 33 OB 109), a spindal drive is provided consisting of a course-pitch thread located inside a hollow piston rod that engages with an outer thread on a shaft-like driving member which is rotatable but not slidable in an axial direction. The construction of such a rotating drive is expensive and, with continued time of use, there is the hazard of contamination and blockage of such a drive system.
The present invention is directed to the objective of eliminating the aforesaid disadvantages by designing a rotating drive of the type mentioned initially above, in that the manufacture of the drive is essentially simplified thus reducing the cost price per unit as well as giving it a far-reaching immunity against being contaminated.